FluentCart Custom order Meta

Can anyone show me a working example of actually displaying custom order fields on the order view. Dev docs here: https://dev.fluentcart.com/hooks/filters/orders-and-payments.html suggest this can be done with this snippet :

add_filter('fluent_cart/order/view', function($order, $data) {
// Add custom data to order view
$order['custom_field'] = 'Custom Value';
return $order;
}, 10, 2);

But I can't get it to work at all.

Anyone have this actually working?